Liquid-gas/air separating devices are used in industry for various applications. For example, in the papermaking field in one instance such a separating device is useful in removing air or gas bubbles from coating liquid which is going to be applied to a moving web of paper. As papermaking techniques and papermaking and coating machines have improved and increased in speed, it has become necessary to provide as air or gas free coating liquid to the paper coaters to prevent gas or air bubble entrainment defects from appearing in the coated paper web or sheet. While there is no problem at say slow speeds, of say 2,000 feet per minute web speeds, when web speeds exceed 3,000 or 4,000 feet per minute and/or approach 6,000 feet per minute or beyond nearly every aspect must be optimized to minimize paper coating defects, and particularly those due to air entrainment in the coating supplied to the coater. While some coaters are not as sensitive to air entrainment problems as others, those coaters that generally are capable of operating at these higher speeds are sensitive to air/gas entrainment. It makes for good paper and coating practice to provide the coater, irrespective of its type, with as gas/air bubble free coating liquid as possible.
Heretofore it has been long known to separate gas or air bubbles from a liquid. For example, see U.S. Pat. No. 3,163,508 which uses the vortex rotation action to separate gas bubbles carried in a liquid. Other means have been used to create the rotational motion which causes the centripetal-centrifugal force resulting in the separation of lighter materials such as gases from heavier materials such as the carrier liquids. One example of such unit is shown in U.S. Pat. No. 5,149,341 which uses a plurality of separating tubes with helical flights therein to cause such rotational motion. In order to achieve adequate flow rate a plurality of separation tubes are frequently ganged together. For example, see U.S. Pat. No. 5,149,341 patent which has the gas entrained liquid entering the bottom of the separating unit with a plurality of separating tubes, each one using the above mentioned helical flights, with the separated gas bubbles being discharged from the top of the separating tubes and the separated liquid also being discharged from the top of the separating tubes and then off to one side of the separating unit.